In recent years, there have been developed various optical fiber measuring modules for measuring the distortion, the temperature or other physical quantity of a structure such as a bridge, a tunnel or a building using characteristics of an optical fiber.
This optical fiber measuring module generally includes an optical fiber core, a cladding, and a covering layer and is adapted to measure the distortion, the temperature or other physical quantity of the optical fiber core by causing a discontinuous pump light such as a laser beam to be incident on the optical fiber core to create a scattered light resulting from the distortion, the temperature and the like of the optical fiber core such as Brillouin scattering or Raman scattering and by detecting the scattered light. Since this optical fiber measuring module can measure a physical quantity at an arbitrary position along the longitudinal direction of the optical fiber core by controlling a sampling timing for detecting the scattered light, it is used for the remote measurement of a distortion, a temperature and the like at an arbitrary position of a structure. Various related technologies have been and are being developed.
For example, Japanese Unexamined Patent Publication No. H09-14927 discloses a technology concerning an optical fiber sensor comprised of a metal tube and a spiral optical fiber held in contact with the inner circumferential surface of the metal tube, and a method for measuring the distortion of a structure using such an optical fiber sensor.
Further, Japanese Unexamined Patent Publication No. 2002-131025 discloses a technology concerning a surface distortion sensor for measuring the distortion of a concrete structure to confirm the progress of a damage of the concrete structure by holding one or more optical fiber cables between sheet-shaped materials through which an adhesive is permeable to fix the optical fiber cables and adhering the resulting sheet to an outer surface of the concrete structure using the adhesive.
However, with the technologies of the above optical fiber measuring module, there are problems of difficulty to rebuild an optical fiber net once this net is cut, and likeliness to damage the optical fiber core required to be carefully handled upon attachment or detachment.
For example, in the case of the technology disclosed in Japanese Unexamined Patent Publication No. H09-14927, it is not easy to attach the metal tube provided with the optical fiber to the structure while aligning it with the structure and the optical fiber core may be damaged if bending or other working is applied to the metal tube.
In the case of the technology disclosed in Japanese Unexamined Patent Publication No. 2002-131025 as well, there are not only a problem that it is not easy to attach and detach the optical fiber measuring module, but also a problem that an excessive load acts on the optical fiber cable upon peeling off the adhered sheet and the optical fiber cores are likely to be damaged since the sheet-shaped optical fiber measuring module is adhered to the outer surface of the concrete structure using the adhesive.
In view of the above problems, an object of the present invention is to provide an optical fiber measuring module which can be easily attached to and detached from a structure, and is free from damaging an optical fiber core required to be carefully handled upon attachment and detachment.